The U.S. Food and Drug Administration (FDA) has granted rare pediatric disease and orphan drug designations for Taysha Gene Therapies’ AAV9-based gene treatment candidate currently in development for epilepsy caused by SLC13A5 deficiency.
SLC13A5, a rate form of infantile epilepsy caused by SLC13A5 gene mutations, is an autosomal recessive disorder characterized by developmental delay as well as seizures that occur within the first few days of life.
The gene therapy company’s TSHA-105 candidate is the AAV9-based gene therapy granted these designations and is poised to be the first treatment for SLC13A5-related epilepsy. There are no currently approved treatments for epilepsy caused by SLC13A5, explained Taysha’s President, Founder and CEO, RA Session II, in a statement. “We are encouraged by the early evidence of TSHA-105’s disease-modifying approach and believe these designations will help us potentially accelerate the development of this exciting program,” said Session. “We look forward to working with the FDA to make TSHA-105 available to patients as expeditiously as possible.”
“We are pleased that the FDA recognizes TSHA-105’s potential as an innovative therapeutic option for SLC13A5 deficiency,” added Rachel Bailey, Ph.D., Assistant Professor in Pediatric Neurology at UT Southwestern. “This disease is a debilitating form of genetic epilepsy in children that significantly impacts movement, motor control, cognition and quality of life, and there remains a need to alter the course of this disease early in life.”
The FDA granted this rare pediatric disease designation due to the disease’s severity and relatively low prevalence in the population. Only diseases and disorders that affect fewer than 200,000 people in the U.S. receive the rare disease designation. Taysha’s TSHA-105 fell under the agency’s Rare Pediatric Disease Priority Review Voucher Program, which aims to “address the challenges that drug companies face when developing treatments for these unique patient populations,” according to the company’s statement about the designations.
The program allows companies to become eligible for a priority review voucher after product approval, which is contingent on whether the marketing application “submitted for the product satisfies certain conditions, including approval prior to September 30, 2026 unless changed by legislation.” Sponsors who are issued a priority review voucher for priority review may redeem this voucher for another marketing application for another candidate.
Taysha Gene Therapies recently teamed up with UT Southwestern Medical Center in Dallas, Texas, to launch an innovation fund that will finance discovery and development of other AAV gene therapies for monogenic diseases involving the central nervous system. And in early January, Taysha partnered with AllStripes to develop an AAV-based gene therapy, TSHA-104, for a rare disorder called SURF1-associated Leigh Syndrome.
Several epilepsy drugs are currently in development by other pharmaceutical companies and are undergoing investigation for both rare and more prevalent forms of epilepsy. Johnson & Johnson’s Actelion, in conjunction with Idorsia Pharmaceuticals, is developing ACT-709478, a selective T-type calcium channel blocker, for patients with photosensitive epilepsy. Another drug being developed by Adamas Pharmaceuticals in collaboration with the Epilepsy Foundation, ADS-4101, is being studied for its effect in focal seizures.
Dravet Syndrome, a rare and drug-resistant form of epilepsy, is also under the spotlight after Epygenix Therapeutics received Orphan Drug Designation for EPX-100 and EPX-200 in 2017. Currently, EPX-100 has advanced through Phase II trials, with a Phase III trial in the works for the near future.
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